1. Digital Hadron Calorimeter (DHCAL) José Repond Argonne National Laboratory CLIC Workshop 2013 January 28 – February 1, 2013 CERN, Geneva, Switzerland

2. J.Repond DHCAL 2 The Digital Hadron Calorimeter (DHCAL) I Active element Thin Resistive Plate Chambers (RPCs) Glass as resistive plates Single 1.15 mm thick gas gap Readout 1 x 1 cm 2 pads 1-bit per pad/channel → digital readout 100-ns level time-stamping Virtually dead-time free Calorimeter 54 active layers 1 x 1 m 2 planes with each 9,216 readout channels 3 RPCs (32 x 96 cm 2 ) per plane Absorber Either Steel or Tungsten

3. J.Repond DHCAL 3 The Digital Hadron Calorimeter (DHCAL) II DHCAL = First large scale calorimeter prototype with Embedded front-end electronics Digital (= 1 – bit) readout Pad readout of RPCs (RPCs usually read out with strips) Extremely fine segmentation with 1 x 1 cm 2 pads DHCAL =World record channel count for calorimetry World record channel count for RPC-based systems 497,664 readout channels DHCAL construction Started in Fall 2008 Completed in January 2011 Test beam activities ~ 5 months in the Fermilab testbeam (Steel absorber) ~ 6 weeks in the CERN testbeams (Tungsten absorber) This is only a prototype For a colliding beam detector multiply by × 50

4. J.Repond DHCAL 4 DHCAL Construction Fall 2008 – Spring 2011 Resistive Plate Chamber Sprayed 700 glass sheets Over 200 RPCs assembled → Implemented gas and HV connections Electronic Readout System 10,000 ASICs produced (FNAL) 350 Front-end boards produced → glued to pad-boards 35 Data Collectors built 6 Timing and Trigger Modules built Assembly of Cassettes 54 cassettes assembled Each with 3 RPCs and 9,216 readout channels 350,208 channel system in first test beam Event displays 10 minutes after closing enclosure Extensive testing at every step

5. J.Repond DHCAL 5 Testing in Beams Fermilab MT6 October 2010 – November 2011 1 – 120 GeV Steel absorber (CALICE structure) CERN PS May 2012 1 – 10 GeV/c Tungsten absorber (structure provided by CERN) CERN SPS June – November 2012 10 – 300 GeV/c Tungsten absorber Test BeamMuon eventsSecondary beam Fermilab9.4 M14.3 M CERN5.6 M23.4 M TOTAL15.0 M37.8 M A unique data sample RPCs flown to Geneva All survived transportation

6. J.Repond DHCAL 6 First R&W Digital Photos of Hadronic Showers Configuration with minimal absorber μ μ120 GeV p 8 GeV e + 16 GeV π + Note: absence of i solated noise hits

7. J.Repond DHCAL 7 Noise studies Several data sets Random trigger runs Trigger-less runs (all hits recorded) Triggered data (first 2/7 time bins) Average noise rate Depends on temperature and ambient pressure Impact on analyses/measurements Noise rate negligible for linearity/resolution Possible effect on shower shape measurements → Requires detailed studies Time distribution of hits far from shower axis Time → N noise = 0.01 ÷ 0.1 hits/event in the entire DHCAL ~15 hits correspond to 1 GeV

8. J.Repond DHCAL 8 Measurements with Muons Performance of the chambers Established through measurement of response to muons Simulation RPC response tuned to reproduce signal from muons DHCAL TCMT

9. J.Repond DHCAL 9 Scan across a single 1 × 1 cm 2 pad x = Mod(x track,1.0) for 0.25 < y < 0.75 y = Mod(y track,1.0) for 0.25 < x < 0.75 Note: these features not explicitly implemented into simulation. Result of properly distributing charge over surface of readout pads

10. 10 Results - October 2010 Data Gaussian fits over the full response curve Unidentified μ's, punch through CALICE Preliminary Fe absorber

11. 11 Pion Selection Standard pion selection + No hits in last two layers (longitudinal containment 16 (off), 32 GeV/c (effects of saturation expected) data points are not included in the fit. N=aE CALICE Preliminary (response not calibrated) Fe absorber

12. 12 Standard pion selection + No hits in last two layers (longitudinal containment) 32 GeV data point is not included in the fit. CALICE Preliminary (response not yet calibrated) B. Bilki et.al. JINST4 P10008, 2009. MC predictions for a large-size DHCAL based on the Vertical Slice Test. Pion Selection Fe absorber

13. 13 CALICE Preliminary (response not yet calibrated) Correction for non-linearity Needed to establish resolution Correction on an event-by-event basis N=a+bE m B. Bilki et.al. JINST4 P04006, 2009. Data (points) and MC (red line) for the Vertical Slice Test and the MC predictions for a large- size DHCAL (green, dashed line). Positron Selection Fe absorber

14. 14 Positron Selection Correction for Non- Linearity Fe absorber

15. 15 Uncorrected for non-linearity Corrected for non-linearity CALICE Preliminary (response not calibrated) Positron Selection Fe absorber

16. J.Repond DHCAL 16 Transportation to CERN Transport fixture Specially built for transportation to CERN Shocks dampened with help of 9 springs Flown to CERN DHCAL cassettes Readout system Gas mixing rack Gas distribution rack Low voltage power supplies High voltage system RPCs Survived transportation to CERN Now back at Argonne (not tested yet)

17. Response at the PS (1 – 10 GeV) Fluctuations in muon peak Data not yet calibrated Response non-linear Data fit empirically with αE β β= 0.90 (hadrons), 0.78 (electrons) W-DHCAL with 1 x 1 cm 2 Highly over-compensating (smaller pads would increase the electron response more than the hadron response) Remember: W-AHCAL is compensating! 17 W absorber

18. Resolution at the PS (1 – 10 GeV) Resolutions corrected for non-linear response Data fit with quadratic sum of constant and stochastic term Particle α c Pions(68.0 ±0.4) %(5.4 ±0.7) % Electrons(29.4 ±0.3) %16.6 ±0.3) % (No systematics yet) 18 W absorber

19. Comparison with Simulation – SPS energies Data Uncalibrated Tails toward lower N hit Simulation Tuned to Fe-DHCAL data (different operating condition) Rescaled to match peaks Shape surprisingly well reproduced 19

20. Response at the SPS (12 – 300 GeV) Fluctuations in muon peak Data not yet calibrated Response non-linear Data fit empirically with αE β β= 0.85 (hadrons), 0.70 (electrons) W-DHCAL with 1 x 1 cm 2 Highly over-compensating (smaller pads would increase the electron response more than the hadron response) 20 W absorber

21. J.Repond DHCAL 21 Institute Argonne National Laboratory IHEP Beijing Boston University CERN COE college Fermilab Illinois Institute of Technology University of Iowa McGill University Northwestern University of Oregon University of Texas at Arlington Contributors to the DHCAL Project

22. J.Repond DHCAL 22 Final Remarks DHCAL performed as expected and validates technical approach DHCAL is a novel detector Many studies ongoing on Calibration (response) Calibration (optimized for resolution) Noise Software compensation… Further R&D needed to design a ‘module 0’ LV/HV distribution Gas distribution and recycling 1-glass RPC design Development of semi-conductive glass (for high rate operation) RPC assembly techniques…